The radiation detectors used in X-ray tomography scanners, e.g. computed tomography scanners, are generally made up of a plurality of detector modules arranged next to one another without interruption. Each detector module has a converter layer, which serves for converting incident X-ray quanta into electrical signals and is structured in a pixel-like fashion in order to obtain a certain spatial resolution. In order to ensure a certain mechanical stability of the detector module, a substrate layer is arranged on the rear side of the converter layer when viewed from the direction that radiation is incident.
Until now, computed tomography scanners have utilized an indirect conversion converter layer as a converter layer. In this type of detector, there is a two-stage conversion of the radiation quanta. In a first stage, the X-ray quanta are absorbed by way of a scintillator and converted into optically visible light pulses. The generated light pulses are subsequently converted into electrical signals in a second stage by way of a photodiode array that is optically coupled to the scintillator. The signals generated thus are usually read out on the rear side of the photodiode array by way of electrical contacts, which are arranged distributed over the area of the photodiode array. Since the substrate layer is also arranged on this side of the photodiode array, the signals must, for further processing, be routed through the substrate layer to readout electronics.
The contacts on the sides of the photodiode array are therefore firstly connected to corresponding first contacts on the substrate layer by adhesive bonding processes or soldering processes and then, within the substrate layer, are routed to corresponding second contacts on the underside of the substrate layer via metallic connections. These second contacts in turn are connected to contact points on a printed circuit board by adhesive bonding processes or soldering processes, which are routed to the readout electronics through circuit-board conductors introduced onto the printed circuit board.
The signal routing between the converter layer and the readout electronics is connected with much production complexity in the case of such an embodiment of a detector module. Moreover, failures of individual signal routings and also the entire detector module have been observed.